1. Field of the Invention
The invention relates to the field of power supplies, particularly power supplies operated from alternating current switched legs.
2. Prior art.
Often in circuits designed to deliver power to, for instance, an incandescent light bulb, a single pole switch is used to complete or interrupt a circuit. Generally, the switch is located remotely from the light bulb with only one of the "hot" power line or neutral line routed to the switch. That is, the switch is mounted apart from a point where both the neutral line and the "hot" line are available without the bulb in one of the lines. This arrangement is referred to as a switched leg. This switched leg is typically adequate except where it is necessary to provide power at the switch itself. When power is required at the switch, current must be drawn through the light bulb to obtain this power. If the switch is in the off position, the current drawn through the bulb may cause the bulb to appear be lighted especially where the bulb is in a dark background.
A circuit for providing power in a switched leg is described in U.S. Pat. No. 4,713,598.